Parabolic Reflection Layer for Backside Illuminated Image Sensors
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Solution Overview
Problem
Existing image sensing devices suffer from energy loss in the wire layer due to incident light not being effectively reflected back to the substrate, particularly when the light wavelength is long or the substrate thickness is insufficient, leading to inefficiencies in energy absorption and potential crosstalk between pixels.
Innovation Solution
A reflection layer with a parabolic surface is disposed on the front side of the substrate in a back side illumination image sensing device, reflecting incident light back into the substrate and preventing it from being reflected into adjacent pixels, thereby increasing absorption and reducing crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If incident light passes through the substrate without reflection, then the device structure is simple, but energy is lost in the wire layer and absorption efficiency is low
Solution Approach 1:
The patent converts the harmful effect of light passing through the substrate and being lost in the wire layer into a beneficial effect by introducing a reflection layer that redirects this light back into the substrate, transforming energy loss into useful light absorption for image sensing
Solution Approach 2:
The reflection layer is pre-configured with a parabolic surface structure before light incidence, which preliminarily determines the light reflection path to return into the substrate, ensuring efficient light absorption before the light interaction process begins
2Object-affected harmful factors
If a flat reflection layer is used, then the device structure is simple, but light is reflected into adjacent pixels causing crosstalk
Solution Approach 1:
The patent applies a parabolic curved surface to the reflection layer instead of a flat surface, which geometrically directs reflected light rays to return to their origin pixel rather than spreading into adjacent pixels, effectively eliminating crosstalk through geometric optics
Solution Approach 2:
Each local region of the parabolic reflection layer is designed with specific curvature characteristics tailored to its position, ensuring that light from each pixel is reflected back to its corresponding pixel region while maintaining overall device functionality
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The parabolic reflection layer enhances light absorption in the substrate, reducing energy loss in the wire layer and minimizing crosstalk between pixels, improving the overall efficiency of the image sensing device.
Implementation Method 1
the reflection layer has a parabolic surface, the incident light can be further prevented from being reflected into other pixels
Implementation Method 2
The image sensing device has a photosensitive element for converting incident light into an electrical signal
Data Source
AI summary
An image sensing device is provided. The image sensing device includes a substrate, a plurality of photosensitive elements, a dielectric layer, a reflector, a color filter, and a microlens structure. The substrate has a first pixel and a second pixel adjacent to the first pixel, and the substrate has a front side and a back side opposite the front side. The photosensitive elements are disposed in the substrate. The dielectric layer is disposed on the back side of the substrate. The reflection is disposed on the front side of the substrate and has a parabolic surface. The color filter layer is disposed on the dielectric layer. The microlens structure is disposed on the color filter layer.